Atomistic modelling of tritium thermodynamics and kinetics in tungsten and its oxides

Abstract

Atomistic simulations using ab initio density functional theory and machine-learned potentials have been employed to map the structural, thermodynamic, and kinetic properties of the T-WOx system (x = 0 to 3). The simulations reveal that the T permeability is low in WO2, intermediate in W, and relatively high in WO3. Diffusion of T is slowest in WO2. Vacancies and self-interstitials are strong traps for T. Oxygen vacancies in WO2 are very strong traps for a few T atoms, while vacancies in bulk W can trap up to ten T atoms. Segregation to WO2 surfaces is energetically favourable. However, segregation of T to WO3 surfaces is energetically unfavourable at high surface coverage.

Keywords

• Tungsten oxides
• Tritium
• Thermodynamic
• Diffusion
• Ab initio
• DFT